Absorption refrigerating apparatus



May 20, ,1952 G. 1'. PIPER BSORPTION REFRGERATING APPRATUS 2sHEETs-SHEET 2 Filed Dec. 24, 1948 ATTORNE Y.

Patented May 20, 1952 ABSORPTION REFRIGERATIN G APPARATUS Glenn T.Piper, Louisville, Ohio, assignor to The Hoover Company, North Canton,Ohio, a corporation of Ohio Application December 24, 1948, Serial No.`67,129

7 Claims. 1

The present invention relates to the art of refrigeration and moreparticularly to a refrigerating apparatus of the pressure equalizedabsorption type arranged to secure most efiicient refrigeratingconditions in the cabinet for preserving sharp frozen food stuifs.

A highly effective utilizaticn of the available storage space within arefrigerator cabinet is realizable by providing for ice freezing and lowtemperature storage in a shallow horizontally eX- tending chamberlocated just beneath the top insulating wall of the cabinetconstruction. Various practical considerations necessitate placing theprincipal cooling element or evaporator of the system in the bottomwall'or on top of the bottom insulating wall of this shallowrefrigerating chamber. 'For purposes of producing ice in theconventional ice tray this is an ideal arrangement as it permits thetrays to be spread out horizontally with their metallic, high heatconducting portions resting directly upon the refrigerated surface. Ithas however been found that this arrangement of low temperaturecompartments has a serious drawback from the standpoint of preservingsharp frozen food stuifs. .In vorder to maintain suiii-ciently lowtemperatures in the upper portion of the shallow compartment to preservesharp frozen food stuffs it is necessary to carry extraordnary lowtemperatures' on the evaporator at temperatures which are not readilyrealizable with the absorption of refrigerating lapparatus particularlyif it is of the three fluid gravity circulation type. The three fiuidpressure equalized type of absorption refrigerating ma; chine possessesan additional disadvantage in Vthis connection in that it is impracticalto place the evaporator at any higher level in the lfood preservingcompartment because of the gravity feed from the condenser to theevaporator. 'If the apparatus is of the type in which the inert gaspositively propels the liquid refrigerant upwardly through theevaporator vthe upperportions of the evaporator are those which arewarmest and hence are not conducive to producing air circulation withinthe storage compartment.

It is a particular obj ect of the present invention to provide arefrigerating apparatus having an upper shallow low temperaturerefrigerating compartment in the upper part ofthe cabinet structure inwhich the main refrigerating effect is concentrated along the uppersurface of the bottom wall of the compartment and in which asupplementary somewhat lower temperature refrigerating effect of mincrcapacity is concentrated in the very topmost portion ofV the regasfiowing counter-current thereto.

frigerated compartment. The foregoing construction provides theconditions which are ideal for the freezing of ice and at the same timeinsures cold air circulation through the storage compartment p forpreserving sharp frozen food stuffs without requiring excessively lowtemperatures in any part of the apparatus. V

It is a further object of the present invention to provide an absorptionrefrigerating apparatus of the pressure) equalized type having aprincipal condenser which Supplies refrigerant to an evaporatorpositioned in the bottom of a low temperature refrigerating compartment,combined with means for revaporizing and recondensing a small amount ofsubstantially pure anhydrous refrigerant from the condensate dischargedfrom the principal condenser and for supplying this refrigerant to asupplementary low temperature evaporator positioned in the top portionof the low temperature refrigerating compartment.

Other objects and advantages of the invention will become apparent asthe description proceeds when taken in connection with the accompanyingdrawings in which:

Figure 1 illustrates a refrigerating apparatus embodying the presentinvention wherein the cabinet structure is shown in Vertical elevationalsection and the refrigerating apparatus is shown partly schematicallyand Figure 2 illustrates a modification of the invention shown inaccordance with the same plan used in the illustration of Figure 1.

Referring now to the drawing in detail and first to Figure 1 thereof,there is illustrated a refrigerating system of the pressure equalizedabsorption type which is charged with a refrigerant such as ammonia, anabsorbent such as water and an inert pressure equalizing medium such ashydrogen.

Heat will be applied by any suitable means, not shown, to the generatorB which contains' a solution of the refrigerant in the absorbent. Heatso applied to the generator evolves refrigerant vapor therefrom whichoperates a vapor lift pump conduit l I to convey the vapor and solutionfrom which refrigerant has been evolved into a gas separation chamber|2. The lean solution is conveyed from the gas separation chamber |2through conduit 13, a liquid heat exchanger hl and a conduit l into theupper end of a tubular air cooled absorber conduit A. The lean solutionflows downwardly through the absorber A in heat exchange relation withcooling air and in contact with a mixture of refrigerant vapor and inertThe solu- 'rectly joins the evaporator 25.

tion absorbs refrigerant vapor from the mixture to produce strongabsorbing solution which then fiowsthrough conduit I'l, reservoir IB,conduit IS, solution heat exchanger |4 and conduit to return to thegenerator B and complete the absorbing solution Circuit.

The inert gas of low refrigerant Vapor content which is formed in theabsorber A is conveyed therefrom through the conduit 22, the innerpassage of the gas heat exchanger G and conduit 23 which opens into alow temperature or supplementary evaporator 25. After traversing theevaporator 25 the inert gas fiows downwardly through the sinuousevaporator conduit 26 and enters the principal evaporator E. Theevaporators 25, 26, and E are each formed of elongated sinuous conduitsarranged in a manner tobe described more fully hereinafter.

After traversing the principal evaporator E, the

inert gas fiows through a conduit 28 into an elongated finned aircooling evaporator conduit` 25. After traversing the conduit 2'9, theinert gas returns to the absorber through 'the conduit 3%, the outerpath of the gas heat exchanger G and the conduit 3| thus completing theinert gas circuit.

The refrigerant Vapor which is separated from absorhing solution in theseparating Chamber l2 fiows through a conduit 33 to the upper portion ofa tubular air cooled condenser C. Condensate formed in the condenser Cfiows through a conduit 3d, having a U-shaped portion to form a liquidfilled gas sealing trap, into a re-evaporating vessel which surroundsthe hot vapo'r conduit 33. The major portion of the refrigerant suppliedto the vessel 35 fiows through a conduit 31 into the gas nlet portion ofthe evaporator E Wherein it meetsand evaporates into the inert gas toproduce refrigeration. The conduit 31 enters the bottom portion of theVessel 35 and then has a vertically extending leg to form a U-shapedliquid filled trap with the Vessel 35 to insure that a major portion ofVessel 35 is fiooded with liquid refrigerant.

A portion of the liquid refrigerant supplied to the vessel 35 isVaporized by heat derived from the hot vapors flowing through theconduit 33. This recties the vapors flowing through the conduit 33 bycondensing absorbent Vapors. The condensate formed in conduit 33 returnsto the separation chamber l2. in the vessel 325 is substantially pureanhydrous annnonia. The pure refrigerant'vapor formed in the yessel 35is oonducted by a conduit 39 to a small tubular air cooled condenser 49wherein it is liqueiied. The liquid foizmed in the condenser flowsthrough a conduit 'iii into that portion of the gas supply conduit 23which di- The quantity 'of refrigerant supplied to evaporator 25 Willvary With Varying designs and specifications; in general, approximately25% of the quantity of liquid condensed in the principal condenser isrevaporized, recondensed and supplied to the low ten peratureevaporator.

The small amount of substantially pure refrigerant applied to theevaporator '25 meets the leanest inert gas in the system hence thisrefrigerant evaporates at a low temperature level and without greatlyenriching the inert gas. As

a oonsequence of this the refrigerating effect proh duced in theevaporators 25 and 25 is in generai at a lower Itemperature than thatproduced in principal evaporator' E. Any refrigerant or other materialwhich may pass through the evaporators 25 and 2d in the liquid statesimply discharges The Vapor evolved into the evaporator E' along withthe inert gas at the point at which it meets the liquid refrigerantsupplied by the conduit 37. Thus the inert gas is partially enriched inthe evaporators 25 and 2d accompanied by production of low temperaturerefrigeration and is further em'iched in the evaporators E and 29accompanied by higher temperature level production of refrigeration.Preferably the system is So proportioned that some liquid refrigerantwill traverse the evaporator E and flow into the evaporator 29 toevaporate at that point for air cooling purposes as Will be describedmore fully hereinafter. Any liquid material which has traversed all ofthe evaporating system without vaporizing is drained from the inert gasdischarge conduit 39 through a trap sealed drain conduit 42 whichdisoharges into the outer or rich gas passage of the gas heat exchangerG.

A vent conduit 4d is connected between the condenser side of the trap inthe vconduit 311 and the disch'arge conduit lii of the conden'ser 40.|Since the conduit does not include a liquid filled gas-trap gaseous andvapor materials supplied thereto can flow directly into the inert gasCircuit along with the liquid.

As shown in Figure 1 the i'efrigei'ating system in general isillustrated schematically except that the relation of the condensers andevaporators to each other and to the refrigerating.cabinetv is shown asa 'complete assembled structure. The refrigerating cabinet comprises aninsulated compartment structure 5% internally divided by an insulatedpartition 5| into an upper low temperature freezing and 'storage Chamber52 and .an air cooling chamber 53. The rear insulated wall 54 of thecabinet structure will be constructed as part of the refrigeratingapparatus andassembled with the cabinet when the refrigeratingvapparatus is secured thereto. Optionally the insulated Wall 5| may be apart of this sub-assembly rather than a part of the principal cabinet.

The evaporator 25 is in the form of a sinuous conduit lying in the verytopmost portion of the compartment '52 and covering the major portion ofthe area thereof. The evaporator coil 26 is in the form of a sinuousconduit lying against the rear wall of the compartment 52 and alsocovering a major portion of the area thereof. The principal evaporator Elies on top of the insulated partition 5| and is in the form of asinuous conduit covering substantially the entire upper surface of thepartition 5 I. A suitable shelf or plate, not shown, will overlie and bemounted to the evaporator E to form a flat surface upon which ice traysor similar articles may be supported. The evaporator 29 is pcsitioned inthe upper rear corner of the compartment E3 in order to refrigerate thesame for the preservation of food stuffs and the like. The evaporator 29will -be proportioned to maintain a temperature of F., for example, andtherebelow, in the compartment 53 which is sufficient for thepreservation of ordinary fresh food stufis Without freezing the same andwithout unduly reducing the humidity within the compartment 53 toproduce undesirable drying of fresh vegetables.

With the above described arrangement the major refrigerating capacityfor low temperature purposes is concentrated in the evaporator E whichoverlies substantially the entire top surface of the insulated partition5| and upon which ice trays and the llike will be seated. By this meansa direct and extensive heat transfer path between the heat conductingportions of ice freezlng trays and' the evaporator is provided which isa most desirable condition for rapid production of ice. The evaporator25 receives the leanest inert gas available in the system and acomparatively small amount of substantially pure anhydrous ammonia henceit operates at aflower temperature and has less capacity thanthe'evaporator E. By placing the colder evaporator l25 in the top of thecompartment 52 circulation of ,air within that compartment is assured,hence food stuifs or other material piled one on top of another will bemaintained at temperatures low enough for safe preservation thereof.

- VA'I'he lower portion of the principal condenser C extends below theevaporator 25, but the condenser 40 is much smaller than condenser C andcan be placed in the customary air cooling compartment atthe rear of thecabinet in position to supply evaporator 25 by gravity withoutextending-above the top wall of the cabinet structure 50.

The trap in the conduit 34 prevents the vapors formed in the evaporatingchamber 35 from passing back to the condenser C. By this means asubstantially fixed proportion of liquid produced in the condenser Cwill always be re-evaporated, recondensed in the condenser 40 andsupplied to the evaporator 25. Because the liquid which is supplied tothe re-evaporating Chamber 35 is liquid ammonia with a minor amount ofabsorb- Vent liquid present as an impurity -the vapors formed in thechamber 35 are almost pure anhydrous ammonia. By so supplying pureammonia to the upper evaporator its function as a lower temperatureelement is facilitated. I

. Referring now to Figure 2 a modified form of the invention isillustrated. This apparatus is ofthe type in which the inert gas ispositively propelled by a mechanical pump and for this purpose it ispreferable to use a dense inert gas such as nitrogen. In this form ofthe invention certain portions of the apparatus are identical withcorresponding portions of the apparatus illustrated in Figure 1; theyare therefore given the same reference character distinguished by theaddition of a prime.

The lean inert gas formed in the air cooled i absorber A' flows througha conduit 60 into the suction side of an electric motor driven gas pump6|. The inert gas is placed under pressure in the pump 6| and isdischarged therefrom into the evaporator 257' through the gas conduit82, the inner passage of the gas heat exchanger G' .and the gas conduit63. The inert gas thus flows through the evaporators 25', 26', E' and29' serially in the order named. After traversing the evaporator 29' theinert gas flows through the conduit 30', the outer -passage of the gasheat exchanger G' and a conduitl 64 which connects to the lower end ofthe absorber A' thus completing the principal inert gas circuit.

The lean absorbing solution formed in the generator B' by the evolutionof refrigerant vapor therefrom flows through the conduit 65, the `liquidheat exchanger |4', the conduit 63 into a reservoir 61. A vent conduit68 connects the upper portion of the reservoir to the rich inert gasreturn conduit 64 which is a low pressure Pumping gas is supplied to thepump conduit 69 below the liquid level maintained therein by thereservoir 61 by means of a conduit 10 which receives inert gas underpressure from the pump discharge conduit 62. The solution flowsdownwardly through the absorber A' in counterflow relationship with andin contact with the inert gas refrigerant vapor mixture supplied to thelower end of the absorber by the conduit 64. The solution absorbsrefrigerant from the inert gas refrigerantvvapor mixture to form richsolution. Rich solution flows out of the lower end of the absorberthrough the conduit 12, liquid heat exchanger |4' and conduit '|3 whichopens into an analyzer 14 mounted upon and in open com.- munication withthe generator B'. The solution traverses the analyzer back to thegenerator thus completing the solution circuit.

The refrigerant vapor evolved in the generator B' traverses theanalyzer14 and then flows through .the conduit 33' in heat exchange relationwith the re-evaporating vessel 35' to the condenser C'. The dualcondenser and reevaporating structure of this form of the invention issubstantially identcal with that described in connection with Figure l.

The substantially anhydrous liquid ammonia recondensed in the condenser43' and supplied to Ithe evaporator 25' through the conduit 4|' meetslean inert gas supplied through the conduit 63 and produces very lowtemperature refrigeration in the evaporators 25' and 26'. The partiallyenriched'inert gas then flows into the evaporator E' wherein it meetsthe princpal body of liquid refrigerant supplied through the` conduit31' from the re-evaporating vessel 35'. Any liquid which is unevaporatedin its path of flow through the evaporator E', conduit 28' andevaporator 29' is drained to the gas heat exarea. Conduit 68 thusmaintains a low pressure in reservoir 81 and also purges the same ofchanger through the trap sealed conduit 42' so that it may return to thesolution circuit through the inert gas return conduit.

The evaporators 25', 26', E' and 29' in this form of the invention willbe arranged identically with the correspondingly numbered evaporators ofthe FigureJ 1 form of the invention and will perform substantially thesame functions. In this form of the apparatus the evaporators may be ofthe type in which the inert gas fiows with a Velocity sufiicient topropel the liquid refrigerant through the evaporators if desired whereasin the Figure 1 form of the apparatus the liquid refrigerantmust'traverse the evaporators under the propulsion of gravity.

In this form of the invention the vent conduit 58 and the connection ofthe conduit 'F2 to the lower end ofV the absorber maintains the gen-.erator analyzer end of the solution circuit at a pressure approachingthe suction pressure of the gas pump 6|. The vent conduit 44' connectsto the discharge conduit 4|' of the condenser 40' adjacent itsconnection to the condenser. The conduit 4|' is U-shaped so as to form aliquid filled gas sealing trap. Uncondensed matter which reachestheconduit 4|' from either condenser is then purged through the ventconduit 1% to the outer passage of the gas heat exchanger G' which isthe richl gas return portion of the apparatus. This venting structuremaintains the condensers at a pressure approaching the suction pressureof the gas pump 6| hence non-condensed matter can fiow freely into thelow pressure side of the inert gas Circuit without the creation of'apressure diiferential which might tend top-draw off large quantities ofVcondensible vapors. Since the condenser-C' and re-evaporating vess'el35' are maintained at a pressure which is lower than thegas pressureprevailing,r in the evaporating system at the junction of the`evaporator and condut 31.' the liquid level will stand in the vessel35' above the point of connection of condut 31' to the evaporator tofbalance the pressure difierential.v

Both forms of the invention realize the advantages of a low heighthoriontally elongatedlow temperature ice freezing and frozen foodstorage compartmcnt in the top portion of Vthe refrigerated cabinet of apressure equalized type refrgerating system. This `is accomp-lished.without extending any portions of the- .apparatus above the top plane ofthe cabinet proper and without creating a condition within the lowtemperature compartment which permits food stufs maintained in the topportion thereof to reach undesirably high temperatures.l The provisionof the low temperature evaporator 25 in the top of the compartmentassures circulatio'n of Yair over stacked up frozen food stus While theprincipal ice freezing load of the system is carried on a flat platetype evaporator structure Aupon which the ice trays may rest so' as tohave maximum eficiency of heat transfer between Water to be frozen andthe large capacity evaporator in the system. This arrangernent is doublyadvantageous because the major portion of t' a compartment such as thecompartment 52 or 52' is required for the purpose of producing ice. Verysmall refrigerating capacity is required to maintain sharp frozen foodstus at safe temperature levels hence the low temperaturerefrigerationproduced by the evaporator 25 and the evaporator E acting in conjunctionwith each other is amply suicient to satisfy this need.

The specific means herein disclosed and cla-imed for condensing therefrigerant evolved in the generator B and for supplying separateportions of the condensate to the evaportors E and 25 is disclosed butnot claimed in the application of Curtis C. Coons, Serial No. 51,554,filed September 28, 1948, and assigned to the assignee of thisapplication.

The attainment of the objectives of this invention through the dualcondenser and re-evaporating chambers 35 or 35' may necessitate asomewhat higher heat imput to the boiler than would be custon'xary withcomparable machines of more conventional design. That is, the vaporsfiowing from the generating assembly through the re-evaporating Chamberheating condut may desirably contain a largerpercenta'ge of vabsorptionsolution vapor than is customary. An appreciable quantity of absorbentvapor can be condensed in the condut 33 or 33' to evolve substantiallypure anhydrous refrigerant vapor for the secondary condenser from thecondensate discharging from the principal condenser.

While I have illustrated and descrbed'the invention in considerabledetail, it is to be understood that Various changes may .be made in thearrangement, proportion and construction of' parts without departingfrom the spirit of the invention or the scope of the appended'claims.

I claim:

1. In a refrigerator, an insulated freezing chamber, a first eva-poratorarranged to refrigerate the lower portion of said chamber, a secondsmaller capacity evaporator arranged to refrigeratc the upper portiono-f said chamber, a generator containing a solution of refrigerant in anabsorbent, a first large air cooled condenser, a

the capacity of o second air cooled condenser of less capacity than saidfirst condenser, condut means for conducting hot vapors from saidgenerator to said -first condenser, a vaporizing jacket surrounding apart of said condut means' condut means including a U-shaped portionforming a liquid retaining trap for conducting condensate from saidfirst condenser to said Jacket, condut meansincludi'ng a liquid filledtrap portion for conveying condensate from said `iacket to said firstevaporator, means for conveying refrigerant vapor from said jaclet tosaid second condenser,V and means for conveying refrigerant liquid fromsaid -=second condenser to said second evaporator;

2; Refrigerating apparatus comprising an insulated cabinet structure, ahorizontal 'partition in said cabinet dividing the interior thereof intoan upper freezing chamber andfa lower food storage chamber, anabsorption refrigeratingapparatus associated with said cabinet structurecomprising a first evaporator arrangedfto refrigerate said freezingChamber adjacentthebottom thereof, a second evaporator arranged toVrefrigerate said -freezing Chamber adjacent'the top thereof, a thirdevaporator arranged to'refrigerate said food storage chamber, agenerator and an absorber connected for circulation of absorptonsolution therebetween, means for circulating inert gas from saidabsorber through' said second and first and third evaporators seria'llyand back to said absorloer,` means for conveyingv hot Vapors from saidgenerator to a first' principal condenser in which vapors are iiquefied,a vaporizing Chamber in heat exchange With a portion of said hot vaporpipe from which condensate can return by rg'ravityl to said generator;means including said vaporizing chamber for'corlveying condensate fromsaid first condenser to said first evaporator includingv meansY toprevent vapor formed in said vaporizing chamber from fiowing through theother portions 'of said conveying means, means for conveying vaporformed in said vaporizing Chamber to said second condenser, means forflowing condensate from said second condenser to said second evaporator,and means for conducting non-condensed matter from said condensers to aportion of the apparatus normally containing inert gas.

3. Refrigerating apparatus of the pressure equalized absorption typeincluding a first evap- Orator, a second evaporator positioned in spacedrelation to said first evaporator, a source of hot refrigerant vapor,first and second condensers, means for conducting refrigerant vapor fromsaid source to said first condenser, means for con- Veying refrigerantliquid from said first condenser through a U-shaped conduit'forming aiiquid filled vapor seal' and l'hence to'said first evaporator in heatexchange withl said=refrigerant vapor conveying means, said' refrigerantliquid conveying means including trap means also to prevent vaporsfo'rmed by said heat exchange from fiowing into said first evaporator,means for conveying refrigerant vapors 'evolved in said last mentionedconveying means to said second condenser, and means for conveyingcondensate from said second condenser to said second evaporator.

4. That method. of producing refrigeration which includes the stepsof'applying heat to a solution of refrigerant in an absorbent to .evolvevapors therefrom, liquefying such vapors to form condensate, passingsaid condensate in heat exchange With said vaporsto evolve substantiallypure refrigerant vapor by vaporizing a portion of said condensate and tocondense non-refrigerant vapor from said first mentioned vapors,condensing said subs'ltantially pure refrigerant vapor separately fromsaid first mentioned vapors to form substantially pure refrigerantliquid, passing solution from which refrigerant has been evolved intocontact with an inert gas refrigerant vapor mixture to absorbrefrigerant vapor therefrom, passing inert gas from which refrigerantvapor has been removed into contact with said substantially purerefrigerant liquid to produce a first ;low temperature refrigeratingeffect, and separably evaporating the remaining portion of said vfirstmentioned condensate into said inert gas which has been enriched byvaporization of saidjsubstantially pure refrigerant liquid to produce asecond higher temperature refrigerating effect.

5. In a refrigeratoif; a cabinet structure having a freezing compartmentoverlying a food storage compartment, a'ifefrigerating apparatusassociated with said oabinet structure comprising a generator andan'absorber connected to form an absorbing solution' circuit, meansforming an inert gas circuit in which inert gas of reduced refrigerantvapor content fiows by gravity from said absorber through a firstevaporator positioned in the top of said freezing compartment and thenthrough a second evaporator positioned in the bottom of said freezingcompartment and then through a third evaporator positioned in said foodstorage compartrfnent, a principal condenser, means for conveyinghotvapors from said generator to a first condenser, means for conveyingcondensate from said first condenser to said second evaporator in heatexchange with said hot vapors flowing to said first condenser, said lastmentioned conveying means including means for preventing vapors formedby said heat exchange from flowing into said first condenser or saidsecond evaporator, a second condenser connected to receive vaporsevolved from condensate discharged from said first condenser and tosupply refrigerant liquid to said first evaporator, and means forrelieving both of said condensers of non-condensible gass''s.

6. Refrigerating 'fapparatus of the pressure equalized absorption`typeincluding a first evaporator, a second evaporator positioned in spacedrelation to said first evaporator, a generator, van absorber, means forcirculating an absorbing solution through said generator and saidabsorber, means for circulating an inert gas through said second andfirst evaporator in that order and back to said absorber, first andsecond condensers,

means for conducting refrigerant vapor from said generator to said firstcondenser, means including a U-shaped conduit connected to said firstcondenser and forming a liquid filled vapor seal for conveyingrefrigerant liquid from said first condenser to said first evaporator inheat exchangeiwith said refrigerant vapor conveying means, means forconveying refrigerant vapors evolved in said last mentioned conveyingmeans to said second condenser, and means for conveying condensate fromsaid second condenser to said second evaporator.

7. In a refrigerator, an insulated freezing chamber, a first evaporatorarranged to refrigerate the lower portion of said chamber, a secondsmalier capacity evaporator arranged to refrigerate the upper portion ofsaid chamber, a generator containing a solution of refrigerant in anabsorbent, an absorber, means for circulatingiiabsorbent lbetween saidabsorber and said generator, means for circulating an inert gas fromsaid absorber through said second and first evaporators and back to saidabsorber, a first air cooled condenser, a second air cooled condenser ofless capacity than said first condenser, conduit means for conductinghot vapors from said generator to said first condenser a vaporizingjacket surrounding a part of said conduit means, conduit means includinga U-shaped conduit forming a liquid retaining trap for conductingcondensate from said first condenser to said jacket, conduit meansincluding a liquid filied trap portion for conveying condensate fromsaid jacket to said first evaporator, means for conveying refrigerantvapor from said jacket to said second condenser, and means for conveyingrefrige'rant liquid from said second condenser to said secondevaporator.

GLENN T. PIPER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,064',233 Thomas Dec. '15, 19362,069,865 Ullstrand Feb. 9, 1937 2,116,998 Ehnbom May 10, 1938 2,194505Kogel et al. Mar. 26, 1940 2,289,078 Schellens et al. July 7, 19422,298,029 Biomqvist Oct. 6, 1942 2,345,505 Siedie Mar. 28, 19442,409,191 Coons May 14, 1946

